i've ridden both the GP5000 TL and the new GP5000 S TR. although i've mounted other tires myself, and fixed flats and all that, i just didn't want to bother with tubeless so i had a shop mount them. can't speak to how hard or easy it was, nobody mentioned anything but shops tend to be pretty good at mounting tires. on my two bikes i've had them on several different wheelsets.
longevity has been excellent for me, 3,000+ miles on a rear and perhaps twice that on a front. they did seem to get squared off pretty fast, but then wore more slowly. no flats. pulled a staple out of my current rear and it went flat over the next few minutes (i wasn't looking.) spun it around a few times, inflated with the hole at the bottom, spun it some more, good as new. love tubeless!
road feel is excellent at 30mm and 32mm; it is a little less "supple" than the 26mm turbo cottons the 30mm ones replaced on my non-electric, but those tires would last <1k miles on a rear for me, so i'm not shedding any tears over a tiny bit more buzz on high frequency pavement. i think they're great tires.
have had good results with both orange seal and stan's.